Systems and methods for removing overspray

ABSTRACT

Systems and methods are disclosed for removing overspray from a substrate. A coating material may be plasma sprayed on a substrate utilizing Suspension Plasma Spray or Solution Precursor Plasma Spray. The plasma spray may deposit loosely adhered overspray on the substrate. A pressurized gas may be directed at the overspray to remove the overspray from the component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a nonprovisional of, and claims priority to, and thebenefit of U.S. Provisional Application No. 61/925,875, entitled“SYSTEMS AND METHODS FOR REMOVING OVERSPRAY,” filed on Jan. 10, 2014,which is hereby incorporated by reference in its entirety.

FIELD

The present disclosure relates generally to plasma spraying. Moreparticularly, the present disclosure relates to systems and methods forremoval of overspray.

BACKGROUND

Suspension Plasma Spray (SPS) and Solution Precursor Plasma Spray (SPPS)processes may be used to apply a coating to components in variousindustries, including components for gas turbine engines. The coatingmay adhere to the components primarily by mechanical forces. During SPSand SPPS processes, overspray generated during the processes may looselyadhere to portions of the components. The overspray may have a weak bondto the underlying material, such that when additional coating is appliedover the overspray, the additional material may be weakly bonded to thecomponent due to the weak bond between the component and the overspray.Overspray bonding may be sufficiently weak that the coating mayprematurely spall during processing or during operation, resulting indiminished performance of the component.

SUMMARY

A method of removing overspray may comprise plasma spraying a substratewith a coating material. The plasma spraying may deposit overspray onthe substrate. The method may further include directing a separatepressurized gas at the overspray, wherein the pressurized gas carries amedia.

A system for coating a substrate may comprise a plasma torch and a gasnozzle. The plasma torch may be configured to deposit a coating materialon a substrate. The gas nozzle may be configured to remove oversprayfrom the substrate.

A method of plasma spraying a substrate may comprise depositing a firstplasma sprayed coating on a first portion of the substrate. The methodmay comprise depositing overspray on a second portion of the substrate.The method may comprise directing pressurized gas at the first portionof the substrate and the second portion of the substrate. Thepressurized gas may remove the overspray from the second portion of thesubstrate. The method may further comprise depositing a second plasmasprayed coating on the second portion of the substrate.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures.

FIG. 1 illustrates a component with a layer of coating material inaccordance with various embodiments;

FIG. 2 illustrates a component with a portion of overspray removed inaccordance with various embodiments;

FIG. 3 illustrates an overspray removal system in accordance withvarious embodiments;

FIG. 4 illustrates a control system with a cam follower in accordancewith various embodiments;

FIG. 5 illustrates gas nozzle coupled to a plasma torch in accordancewith various embodiments; and

FIG. 6 illustrates a flow diagram of a process for removing overspray inaccordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of various embodiments herein makes referenceto the accompanying drawings, which show various embodiments by way ofillustration. While these various embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosure, it should be understood that other embodiments may berealized and that logical, chemical, and mechanical changes may be madewithout departing from the spirit and scope of the disclosure. Thus, thedetailed description herein is presented for purposes of illustrationonly and not of limitation. For example, the steps recited in any of themethod or process descriptions may be executed in any order and are notnecessarily limited to the order presented. Furthermore, any referenceto singular includes plural embodiments, and any reference to more thanone component or step may include a singular embodiment or step. Also,any reference to attached, fixed, connected, or the like may includepermanent, removable, temporary, partial, full, and/or any otherpossible attachment option. Additionally, any reference to withoutcontact (or similar phrases) may also include reduced contact or minimalcontact.

Systems and methods are disclosed herein for removing overspray from acomponent. A plasma torch may deposit a coating material onto acomponent. During deposition of the coating material, a portion of thedeposited material termed “overspray” may be loosely adhered to thecomponent. The overspray may be loosely adhered to the componentadjacent to an intended coating surface.

The overspray may be a result of fine particles or media present in theSPS or SPPS processes. The trajectory that fine particles take in theprocess may be influenced by the plasma gases more so than with heavierparticles in traditional plasma spray processes. As the plasma gasesapproach the component, the plasma gases may spread out and/or deflectaway from the target point of the plasma torch. The plasma gases at theedges of the plasma jet may follow a longer mean path before contactingthe surface of the component. Fine particles carried by the plasma gasesat the edges of the plasma jet may thus interact with the atmosphere forlonger time and cool off disproportionately compared to fine particlesin the center of the plasma jet. The fine particles may therefore becooler at the point of contact with the component and may be less ableto deform and bond with the target surface. The result may be a weakbond to the component at locations farther away from the center of theplasma jet. The overspray may additionally be caused by a lack ofentrainment of the particulate within the plasma plume. The fineparticles may not penetrate the plume effectively and may flow along theoutside of the plasma plume.

A gas nozzle may direct pressurized gas at the component in order toremove the overspray. The pressurized gas may carry solid particleswhich may contact the component. Once the overspray is removed, theplasma torch may deposit additional coating material to the cleanedsurface which may sufficiently adhere to the component.

Referring to FIG. 1, a component 100 with a layer of coating material110 is illustrated according to various embodiments. A plasma spraysystem may deposit coating material 110 onto component 100. Component100 may comprise any type of component for which a plasma sprayedcoating may be desirable. In various embodiments, component 100 maycomprise a component of a gas turbine engine, such as a turbine blade,turbine vane, blade outer air seal, or combustor component. However,components suitable for use with the present disclosure may be found inmany industries and are not limited to those recited herein.

Coating material 110 may improve properties of component 100. In variousembodiments, coating material 110 may comprise a thermal protectivelayer. Various coating materials may improve functional performance ofcomponent 100, improve the component life by reducing abrasion orcorrosion, and may allow higher cost materials with advantageousproperties to be utilized on a lower cost material which forms thestructure of component 100.

In various embodiments, coating material 110 may be deposited ontocomponent 100 using a Suspension Plasma Spraying (“SPS”) process. SPSinvolves dispersing a ceramic feedstock into a liquid suspension priorto injecting the feedstock into a plasma jet. In various embodiments,coating material 110 may be deposited using a Solution Precursor PlasmaSpray (“SPPS”) process, in which a solution of coating precursors isatomized and injected into a direct current (DC) plasma jet. Theprecursor droplets may evaporate and breakup in the plasma. Variousmaterials may be plasma sprayed onto component 100. In variousembodiments, coating material 110 may comprise a rare earthpartially-stabilized zirconia, such as yttria-stabilized zirconia, arare earth stabilized zirconia, such as gadolinium stabilized zirconia,or any other material suitable for plasma spraying onto component 100.

During deposition of coating material 110, overspray 120 may bedeposited onto component 100 adjacent to coating material 110. Overspray120 may be loosely adhered to component 100, and removal of overspray120 may be desirable prior to depositing additional coating material inthe area of overspray 120.

Referring to FIG. 2, component 100 is illustrated with a portion ofoverspray 120 removed. In various embodiments, overspray 120 may beremoved by directing a pressurized gas at component 100. The pressurizedgas may contact component 100 at a kinetic energy sufficiently high toremove overspray 120, yet sufficiently low to not remove coatingmaterial 110. In various embodiments, the kinetic energy may besufficiently higher than the amount of energy to bond the overspray tothe underlying surface, but less than the energy to bond the targetmaterial to the underlying surface so as to preferentially remove thematerial from the overspray region. As illustrated in FIG. 2,pressurized gas has been directed across area 210, such that overspray120 is removed from component in area 210, and such that coatingmaterial 110 remains on component 100 in area 210.

In various embodiments, the pressurized gas may comprise at least one ofcarbon dioxide, nitrogen (N₂), argon, other noble gases, water vapor,compressed air, or any other suitable gas. In various embodiments, thepressurized gas alone may be sufficient to remove overspray 120.However, in various embodiments, the pressurized gas may carry a mediato add kinetic energy or otherwise assist in removing the overspray. Invarious embodiments, the media may exist as a gas at standardtemperature and pressure (STP), such that removal of the media may notbe required after removal of the overspray. In various embodiments, themedia may comprise dry ice (carbon dioxide) particles which maysublimate after removal of the overspray. In various embodiments, themedia may comprise liquid nitrogen which may evaporate after removal ofthe overspray.

In various embodiments, the media may comprise a liquid. The pressurizedgas may be at a higher temperature than the boiling point of the liquid.In various embodiments, the media may comprise water droplets, and thepressurized gas may be at a temperature higher than 100° C. (212° F.).The water droplets may be in the pressurized gas for a short time beforecontacting the component, such that the water droplets contact thecomponent prior to evaporating, and evaporate after removing theoverspray.

In various embodiments, the pressurized gas may comprise particulatematter such as polymer beads, alumina powder, silicon carbide powder,glass beads, walnut shells, sodium bicarbonate, sodiumbicarbonate/alumina blend, or any other suitable abrasive media that mayremove the overspray but not significantly alter dimensions of thecomponent, interfere with coating adhesion, or alter the bond coatsurface finish.

Referring to FIG. 3, an overspray removal system 300 is illustratedaccording to various embodiments. Overspray removal system may comprisea gas nozzle 310 or series of nozzles directed at the overspray to beremoved. Gas nozzle 310 may direct pressurized gas 312 toward acomponent 320. Gas nozzle 310 may be positioned with a control system330. In various embodiments, control system 330 may comprise roboticsand/or one or more servo motors or cam followers. Control system 330 maybe designed to optimize the standoff distance of gas nozzle 310 from thesurface of which the overspray is to be removed. In various embodiments,overspray removal system 300 may comprise a plurality of gas nozzles310, and a plurality of solenoid valves which may turn gas nozzles 310on/off as necessary to target the appropriate surfaces of component 320and to maximize the effectiveness of overspray removal while controllingand/or reducing gas usage in the process.

In various embodiments, control system 330 may comprise a distance meter340. In various embodiments, distance meter 340 may comprise a laserdistance meter. As component 320 rotates about axis of rotation 322, astandoff distance D between gas nozzle 310 and component surface 324 maychange. Distance meter 340 may detect a change in distance and maytransmit the information to control system 330. In response, controlsystem 330 may move gas nozzle 310 such that standoff distance D remainssubstantially constant. In various embodiments, control system 330 maycomprise two axis control of gas nozzle 310, three axis control of gasnozzle 310, or any number of axes.

In various embodiments, a pressure of the pressurized gas 312 may dependon a variety of factors, such as the standoff distance D, the type ofgas and/or particulate matter being used, and a nozzle size. In variousembodiments, gas carrying dry ice particles may be pressurized tobetween 20 psi-90 psi (140 kPA-620 kPa), and a standoff distance D maybe between 4 inches-15 inches (10 cm-38 cm). A nozzle diameter may bebetween 0.2 inches-1.0 inches (0.51 cm-2.5 cm). In various embodiments,the pressurized gas may exit gas nozzle 310 at speeds of between aboutMach 1.5-Mach 2.5 (510 m/s-850 m/s). However, in various embodiments,any combination of pressure, standoff distance, gas type, and nozzlesize may be used wherein the kinetic energy of the pressurized gas issufficient to remove overspray yet not remove the coating material.

Referring to FIG. 4, in various embodiments, control system 400 maycomprise a cam follower 410. Cam follower 410 may comprise a shaft 412coupled to a roller 414 in contact with the component 320 being coated.Component 320 may be rotated on a turntable or carousel. As component320 rotates, contact between component 320 and roller 414 may forceshaft 412 away from the axis of rotation 322 of component 320. A springmay be coupled to shaft 412 which maintains pressure on shaft 412 in thedirection of axis of rotation 322 of component 320.

In various embodiments, gas nozzle 310 may be coupled to shaft 412. Gasnozzle 310 may be coupled to shaft 412 at an optimized standoff distanceD from component 320. Thus, as component 320 rotates, gas nozzle 310 maymove with shaft 412 and maintain the desired standoff distance fromcomponent 320.

Referring to FIG. 5, in various embodiments, gas nozzle 310 may becoupled to plasma torch 500. Plasma torch 500 may be controlled by arobotic system 510 in order to deposit coating material. Gas nozzle 310may be located at a fixed distance D2 from plasma torch 500. In variousembodiments, plasma torch 500 and gas nozzle 310 may simultaneouslydeposit coating and remove overspray, respectively. However, in variousembodiments, plasma torch 500 may deposit coating material, and roboticsystem 510 may subsequently direct gas nozzle 310 to remove overspraydeposited by plasma torch 500. Plasma torch 500 may then depositadditional coating material where gas nozzle 310 has cleaned oversprayfrom component 320.

Referring to FIG. 6, a flowchart of a process 600 for removing oversprayis illustrated according to various embodiments. A first layer ofcoating material may be plasma sprayed onto a substrate (step 610). Theplasma spray may further deposit overspray on the substrate. Apressurized gas may be directed at the overspray (step 620). Thepressurized gas may remove the overspray from the substrate. A secondlayer of coating material may be plasma sprayed where the overspray wasremoved (Step 630).

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

1. A method of removing overspray comprising: plasma spraying asubstrate with a coating material, wherein the plasma spraying depositsan overspray on the substrate; and directing a separate pressurized gasat the overspray, wherein the pressurized gas carries a media.
 2. Themethod of claim 1, wherein the pressurized gas removes the oversprayfrom the substrate.
 3. The method of claim 1, wherein the plasmaspraying comprises at least one of a suspension plasma spray and asolution precursor plasma spray.
 4. The method of claim 1, wherein thepressurized gas comprises at least one of carbon dioxide, nitrogen,argon, water vapor, and compressed air.
 5. The method of claim 1,wherein the media comprises at least one of dry ice particles, water,liquid nitrogen, polymer beads, alumina powder, silicon carbide powder,glass beads, walnut shells, sodium bicarbonate, and sodiumbicarbonate/alumina blend.
 6. The method of claim 1, wherein thepressurized gas contacts the substrate with a kinetic energy sufficientto remove the overspray and insufficient to remove the coating material.7. The method of claim 1, further comprising plasma spraying thesubstrate after directing the pressurized gas at the overspray.
 8. Themethod of claim 1, further comprising determining a standoff distancebetween a gas nozzle and the substrate.
 9. The method of claim 1,wherein the media at least one of sublimates and evaporates at standardtemperature and pressure.
 10. The method of claim 1, wherein the coatingis deposited with a plasma torch, and wherein the pressurized gas issprayed with a gas nozzle.
 11. The method of claim 10, wherein the gasnozzle is coupled to the plasma torch.
 12. A system for coating asubstrate comprising: a plasma torch configured to deposit a coatingmaterial on a substrate; and a gas nozzle configured to remove oversprayfrom the substrate.
 13. The system of claim 12, further comprising apositioning control system coupled to the gas nozzle.
 14. The system ofclaim 12, wherein the plasma torch is configured to utilize at least oneof a suspension plasma spray and a solution precursor plasma spray. 15.The system of claim 12, further comprising a gas supply coupled to thegas nozzle.
 16. The system of claim 15, wherein the gas supply comprisesat least one of carbon dioxide, nitrogen, argon, water vapor, andcompressed air.
 17. The system of claim 12, wherein the gas nozzle isconfigured to direct dry ice particles at the substrate.
 18. The systemof claim 12, further comprising a control system, wherein the controlsystem is configured to maintain a standoff distance between the gasnozzle and the substrate.
 19. The system of claim 12, wherein the gasnozzle is one of a plurality of gas nozzles configured to removeoverspray from the substrate.
 20. A method of plasma spraying asubstrate comprising: depositing a first plasma sprayed coating on afirst portion of the substrate; depositing overspray on a second portionof the substrate; directing pressurized gas at the first portion of thesubstrate and at the second portion of the substrate, wherein thepressurized gas removes the overspray from the second portion of thesubstrate; and depositing a second plasma sprayed coating on the secondportion of the substrate.